In this part, I'll present you with the most common techniques, the ones I use most often; however, please don't consider this list to be exhaustive.
This is probably the easiest technique of all. It's not very effective, it cannot be used everywhere, and it requires access to both the source code and a Terminal that will run it (and therefore show the results of the print function calls).
However, in many situations, this is still a quick and useful way to debug. For example, if you are developing a Django website and what happens in a page is not what you would expect, you can fill the view with prints and keep an eye on the console while you reload the page. When you scatter calls to print in your code, you normally end up in a situation where you duplicate a lot of debugging code, either because you're printing a timestamp (like we did when we were measuring how fast list comprehensions and generators were), or because you have somehow to build...